Virus-thwarting mosquitoes decline on Vietnamese island

Scientists plan to release second generation of mosquitoes that suppress dengue

Disease-blocking mosquitoes that were poised to take over a Vietnamese island appear to be dying off, according to recent results.

The mosquitoes, which scientists released from April to September, carry Wolbachia bacteria. The bacterial infection spreads among mosquitoes and prevents the insects from transmitting the dengue virus. Dengue causes painful fevers in people.

In November, the infected insects accounted for 65 percent of the island’s mosquito population (SN Online: 11/19/13). Scientists estimate that if Wolbachia-infected mosquitoes reach 80 percent, they could eliminate cases of dengue fever on the island. But in the latest survey results, reported the week of December 8, the mosquitoes had slipped to 50 percent of the population.

"This particular Wolbachia strain is not spreading into the wild mosquito population as we had hoped,” says lead researcher Scott O’Neill of Monash University in Clayton, Australia.

O’Neill suspects that the strain of Wolbachia used in the trial made the mosquitoes too sickly. He and his colleagues are readying new, healthier mosquitoes infected with a different strain of Wolbachia­ to test on the island.